Vertical resolution of baroclinic modes in global ocean models

Stewart, Kial Douglas; Hogg, Andrew McC.; Griffies, Stephen M.; Heerdegen, Aidan; Ward, Marshall L.; Spence, Paul; England, Matthew H.

doi:10.1016/j.ocemod.2017.03.012

Cited by 94 publications

(98 citation statements)

References 48 publications

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“…This gives a balance between high resolution near the surface to resolve short-term ocean responses to atmospheric forcing and reasonable resolution in the thermocline. Stewart et al (2017) show that 75 levels is the minimum number capable of resolving the second baroclinic mode. Cells spanning partial model levels are allowed next to the bathymetry (Barnier et al, 2006;Adcroft et al, 1997).…”

Section: Model Grid and Bathymetrymentioning

confidence: 92%

UK Global Ocean GO6 and GO7: a traceable hierarchy of model resolutions

et al. 2018

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Abstract. Versions 6 and 7 of the UK Global Ocean configuration (known as GO6 and GO7) will form the ocean components of the Met Office GC3.1 coupled model and UKESM1 earth system model to be used in CMIP6 1 simulations. The label "GO6" refers to a traceable hierarchy of three model configurations at nominal 1, 1/4 and 1/12• resolutions. The GO6 configurations are described in detail with particular focus on aspects which have been updated since the previous version (GO5). Results of 30-year forced ocean-ice integrations with the 1/4 • model are presented, in which GO6 is coupled to the GSI8.1 sea ice configuration and forced with CORE2 2 fluxes. GO6-GSI8.1 shows an overall improved simulation compared to GO5-GSI5.0, especially in the Southern Ocean where there are more realistic summertime mixed layer depths, a reduced near-surface warm and saline biases, and an improved simulation of sea ice. The main drivers of the improvements in the Southern Ocean simulation are tuning of the vertical and isopycnal mixing parameters. Selected results from the full hierarchy of three resolutions are shown. Although the same forcing is applied, the three models show large-scale differences in the near-surface circulation and in the short-term adjustment of the overturning circulation. The GO7 configuration is identical to the GO6 1/4 • configuration except that the cavities

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Section: Model Grid and Bathymetrymentioning

confidence: 92%

UK Global Ocean GO6 and GO7: a traceable hierarchy of model resolutions

et al. 2018

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“…For the mesoscale, Stewart et al. () proposed that the vertical grid be sufficiently refined to resolve the baroclinic modal structure for those modes admitted by the horizontal grid. They estimate that 50 well‐positioned vertical degrees of freedom are sufficient for a model resolving the first baroclinic mode, and 75 for the second mode.…”

Section: Framing the Om4 Developmentmentioning

confidence: 99%

The GFDL Global Ocean and Sea Ice Model OM4.0: Model Description and Simulation Features

Adcroft

Anderson

Balaji

et al. 2019

J Adv Model Earth Syst

298

361

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We document the configuration and emergent simulation features from the Geophysical Fluid Dynamics Laboratory (GFDL) OM4.0 ocean/sea ice model. OM4 serves as the ocean/sea ice component for the GFDL climate and Earth system models. It is also used for climate science research and is contributing to the Coupled Model Intercomparison Project version 6 Ocean Model Intercomparison Project. The ocean component of OM4 uses version 6 of the Modular Ocean Model and the sea ice component uses version 2 of the Sea Ice Simulator, which have identical horizontal grid layouts (Arakawa C‐grid). We follow the Coordinated Ocean‐sea ice Reference Experiments protocol to assess simulation quality across a broad suite of climate‐relevant features. We present results from two versions differing by horizontal grid spacing and physical parameterizations: OM4p5 has nominal 0.5° spacing and includes mesoscale eddy parameterizations and OM4p25 has nominal 0.25° spacing with no mesoscale eddy parameterization. Modular Ocean Model version 6 makes use of a vertical Lagrangian‐remap algorithm that enables general vertical coordinates. We show that use of a hybrid depth‐isopycnal coordinate reduces the middepth ocean warming drift commonly found in pure z* vertical coordinate ocean models. To test the need for the mesoscale eddy parameterization used in OM4p5, we examine the results from a simulation that removes the eddy parameterization. The water mass structure and model drift are physically degraded relative to OM4p5, thus supporting the key role for a mesoscale closure at this resolution.

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“…Both ocean configurations have 47 unevenly spaced vertical z levels, which is nearly sufficient to resolve the first baroclinic mode (see, e.g., Stewart et al, 2017). The Gent-McWilliams (GM) parameterization (Gent & Mcwilliams, 1990) for eddy transport is used, with maximum diffusivity of 1,500 m 2 /s.…”

Section: Model Setupsmentioning

confidence: 99%

The Relative Influence of Atmospheric and Oceanic Model Resolution on the Circulation of the North Atlantic Ocean in a Coupled Climate Model

Sein

Koldunov

Danilov

et al. 2018

J Adv Model Earth Syst

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It is often unclear how to optimally choose horizontal resolution for the oceanic and atmospheric components of coupled climate models, which has implications for their ability to make best use of available computational resources. Here we investigate the effect of using different combinations of horizontal resolutions in atmosphere and ocean on the simulated climate in a global coupled climate model (Alfred Wegener Institute Climate Model [AWI‐CM]). Particular attention is given to the Atlantic Meridional Overturning Circulation (AMOC). Four experiments with different combinations of relatively high and low resolutions in the ocean and atmosphere are conducted. We show that increases in atmospheric and oceanic resolution have clear impacts on the simulated AMOC, which are largely independent. Increased atmospheric resolution leads to a weaker AMOC. It also improves the simulated Gulf Stream separation; however, this is only the case if the ocean is locally eddy resolving and reacts to the improved atmosphere. We argue that our results can be explained by reduced mean winds caused by higher cyclone activity. Increased resolution of the ocean affects the AMOC in several ways, thereby locally increasing or reducing the AMOC. The finer topography (and reduced dissipation) in the vicinity of the Caribbean basin tends to locally increase the AMOC. However, there is a reduction in the AMOC around 45°N, which relates to the reduced mixed layer depth in the Labrador Sea in simulations with refined ocean and changes in the North Atlantic current pathway. Furthermore, the eddy‐induced changes in the Southern Ocean increase the strength of the deep cell.

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Vertical resolution of baroclinic modes in global ocean models

Cited by 94 publications

References 48 publications

UK Global Ocean GO6 and GO7: a traceable hierarchy of model resolutions

UK Global Ocean GO6 and GO7: a traceable hierarchy of model resolutions

The GFDL Global Ocean and Sea Ice Model OM4.0: Model Description and Simulation Features

The Relative Influence of Atmospheric and Oceanic Model Resolution on the Circulation of the North Atlantic Ocean in a Coupled Climate Model

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